Immersed tube method-based tunnel construction is to respectively transport tunnel immersed tubes, which are prefabricated in a semi-submerged barge or a dry dock, in a floating manner to preset positions for immersion and jointing. In order to successfully immerse the last tube section, a distance space longer than the tube section must be reserved, and the tube section immersed and jointed in the reserved distance space is regarded as a final joint, namely two ends connected with a tunnel are immersed and are jointed and closed in the sea, and a finally closed tube section is the final joint. The existing final joints are all integrated active water stop final joints, and have lengths conforming to a distance (which is generally within 30 meters in length) between two sections of immersed tunnels. All the final joints are independently designed, and are different from common tube sections (which have lengths more than 100 meters); and respective foundations for immersing and supporting the final joints and foundations for the common tube sections have a rigidity difference, which may cause non-uniform settlement of the final joints and the common tube sections during operation of a subsea tunnel, and cause a damage to the subsea tunnel.